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Redirect Callback Validator
x402
Redirect Callback Validator is a paid API for AI agents from phion.systems, paid per call via x402, $0.002/call, status unknown (last checked 2026-09-14).
Validates HTTPS callback and redirect destination URLs against an explicit host allowlist to prevent open redirect and SSRF attacks
Price / call$0.002
Success—
StatusUnknown
How this service works
Validate HTTPS callback and redirect destinations against an explicit host allowlist
Output
A validation decision indicating whether the callback or redirect destination URL matches an entry on the provided host allowlist, including which host was checked, whether it was approved or rejected, and any policy violations detected.
Example use cases
OAuth callback safety check
“I'm about to receive an OAuth callback to https://auth.myservice.com/oauth/callback — can you verify that host is on my allowlist [auth.myservice.com, login.myservice.com] before I process the token?”
Agent webhook destination guard
“My agent is about to send results to a webhook at https://hooks.partner.io/receive — validate that against my permitted hosts [hooks.partner.io, api.partner.io] so I know it's not being redirected somewhere unauthorized.”
Payment redirect validation
“Before redirecting the user after checkout to https://shop.acme.com/thankyou, check that destination against my approved redirect hosts [shop.acme.com, www.acme.com] and tell me if it's safe.”
Technical details
Endpoint
POSThttps://phion.systems/v1/paid/trust/redirect-callback-validatorWhen to prefer
Use this endpoint when an agent or automated workflow must follow a redirect or invoke a callback URL and needs a signed, auditable decision that the destination is authorized — especially in OAuth flows, payment callbacks, webhook dispatching, or any scenario where an attacker could manipulate the redirect target to cause open redirect or SSRF attacks. Prefer this over ad-hoc string matching when you need an explicit allowlist enforcement record.
Side effects
- URL not on allowlist — returns rejection with the offending host
- Malformed or non-HTTPS URL — returns validation error
- Empty or missing allowlist — returns policy configuration error
- Subdomain mismatch when exact-host matching is enforced — returns rejection
- Network timeout or service unavailability — returns 5xx error
Input
Schema · Request body
{
"$schema": "https://json-schema.org/draft/2020-12/schema",
"type": "object"
}Tags
x402
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